PURPOSE: To reduce working time by providing a work in the direction where laser light is oscillated and outputted from a laser oscillator so as to face said oscillator and selecting a suitable focusing lens in accordance with working conditions and the material of the work.

CONSTITUTION: A work 12 is provided in the direction where laser light is oscillated and outputted from a laser oscillator 1 so as to face said oscillator. A control device 19 feeds a signal to a motor 6 in compliance with the program predetermined according to the material, working shape, etc. of the work 12. The motor 6 moves a member 4 for fixing a focusing lens to select the lens for focusing the laser light from the oscillator 1 among the focusing lenses 3a, 3b, 3c attached to the member 4. Laser working is executed in the above-mentioned way.